Polarized photoelectric switching system



Fe 1, 1966 G. T. SENSENEY POLARIZED PHOTOELECTRIC SWITCHING SYSTEM FiledNov. 14, 1962 FIG INVENTOR. GfO/ifif I JHVSMH United States Patent3,233,110 POLARIZED PHOTOELECTRIC SWITCHING SYSTEM George T. Senseney,New York, N.Y., assignor to White Avionics Corporation, Plainview, N.Y.,a corporation of New York Filed Nov. 14, 1962, Ser. No. 237,670 Claims.(Cl. 250209) The present invention relates to an electrically controlledswitching system having no moving parts and an exceptionally high speedof response.

Electrical control of switch action is common. Perhaps the most commoninstrumentality operating on this principle is the electromagneticrelay, in which electrical energization of a winding causes magneticattraction of an armature, the movement of the armature actuatingmechanical switch contacts. Such devices, although in very widespreaduse, have certain inherent drawbacks-their time of response is limitedbecause movement of mechanical parts is required, their sensitivity islimited be cause of the mass (inertia) of those mechanical parts, andtheir longevity is limited because of the wear incident upon mechanicalmovement and the engagement and separation of current-carrying contacts.

Various types of electronic systems have been devised which avoid thedisadvantages inherent in mechanical movement. These electronic systemsprovide a great decrease in switching time, but in many instances theyinvolve relatively complex circuitry and the use of troubleproneelectronic components.

It is the prime object of the present invention to devise a simplesystem for controlling the switching of external circuits, which systemhas an exceptionally high speed of response, involves no moving parts,and is exceptionally simple and reliable. The system of the presentinvention is specially adapted to be sensitive to the polarity of theinput signal, actuating the output circuits in a given way when thepolarity of the input signal is of a given sense and actuating theoutput circuits in a different way when the polarity of the input signalis of the opposite sense. It is a further prime object of the presentinvention to devise such a system in which the controlling parts areincorporated into a sturdy, simple and small assembly.

In accordance with the present invention the instrumentalities whichactually carry out the switching operation are light-sensitive elements,and the actuation of those elements is accomplished by controlling thelight which impinges upon them. A pair of light-sensitive elements areprovided, each preferably controlling a different utilization circuit.The light source is in the form of a glow discharge tube having firstand second electrodes and having the characteristic that only one ofsaid electrodes glows at a time depending upon the polarity of the DJC.energization applied to the tube. Each of the light sensitive elementsis associated in a light-transmissive sense with a dilfere-nt one of theglow discharge tube electrodes, so that when a given one of thoseelectrodes glows a significant amount of light reaches only that lightsensitive element operatively associated therewith. In this way one orthe other of the light-sensitive elements is actuated, depending uponthe polarity of the electrical signal applied to the glow dischargetube. When, as is preferred, the light-sensitive elements have aninherent latching efiect (when once rendered conductive by theimpingement of light thereupon, they will remain conductive for as longas appropriate potential is applied thereto), a commutating capacitormay be associated with those elements, so that when one is renderedconductive the other is rendered non-conductive.

More specifically, a polarized photoelectric assembly 3,233,110 PatentedFeb. 1, 1966 is produced which comprises a housing having an aperture inwhich a glow discharge tube of the type described is mounted. A pair oflight-transmissive paths are formed in that housing, each extending froma different electrode of the glow discharge tube to a station(preferably an aperture) where a light sensitive element is mounted. Thelight transmissive paths are specifically disclosed as being defined byslots formed in the housing and extending from the glow discharge tubeaperture to the light-sensitive element stations, the walls and/ or bodyof the housing being sufiiciently opaque so that light emanating from agiven glow discharge tube electrode, when it glows, passes substantiallyonly to the particular light-sensitive element associated therewith. Theentire assembly of housing, glow discharge tube and light-sensitiveelements comprises a small, sturdy and protected unit. Appropriateelectrical connections to the operative elements may readily be made.The resultant system has no moving parts, there is no bounce or chatter,such as characterize mechanical relays, no magnetic fields aredeveloped, as in magnetic relays, which might adversely affectassociated circuits, and the operative parts may be encapsulated orotherwise protected so as to be exceptionally resistant to vibrations,shock, high temperature, humidity, corrosive atmospheres and the like.

To the accomplishment of the above, and to such other objects as mayhereinafter appear, the present invention relates to the construction ofa photoelectric assembly and a photoelectrically controlled switchingsystem, all as defined in the appended claims and as described in thisspecification, taken together with the accompanying drawings, in which:

FIG. 1 is a top plan view of a preferred embodiment of the presentinvention;

FIG. 2 is a cross sectional view taken along the line 2-2 of FIG. 11;and

FIG. 3 is a circuit diagram illustrating a preferred man ner in whichthe assembly of FIGS. 1 and 2 may be used.

The polarized photoelectric assembly of the present invention comprisesa housing generally designated 2 of any suitable material, such aselectrically insulating plastic. An aperture 4 is formed in the housing2 and two slots 6 and 8 extend in opposite directions from the aperture4 to apertures 10 and 12 respectively. A glow discharge tube '14 ismounted in any appropriate manner in the aperture 4. This tube isprovided with electrodes 16 and 18 which extend out from the tube 14 andto which appropriate electrical connections may be made, as describedmore in detail below. The tube 14 has the characteristic that whenappropriate D.C. energizat-ion is applied to the electrodes '16 and 18,only one of those electrodes will glow, depending upon the polarity ofthat energization. For example, when the tube 14 is in the form of aneon lamp, only that one of the electrodes 16 and 18 which is thecathode will glow. Moreover, with a tube of that type, and when anappropriate potential difference is applied across the electrodes 16 and18, that electrode which is the cathode will glow virtuallyinstantaneously with the application of appropriate electricalenergization thereto. The tube 14 is so positioned within the aperture 4that each of its electrodes 16 and 18 is operatively opticallyassociated with a different one of the slots 6 and 8. As herespecifically disclosed the electrode 16 is positioned opposite the innerend of the slot 6 and the electrode 18 is positioned opposite the innerend of the slot 8.

Light sensitive elements 26 and 22 are mounted in any appropriate mannerin the apertures 10 and 12 respectively so as to be operativelyoptically associated with light passing through the slots 6 and 8respectively. The light-sensitive elements 26 and 22, in the form herespecifically disclosed, comprise PNPN silicon diodes Zita and 22arespectively encased within transparent housings 29b and 22b and havingleads 26c, 20d and 22c, 22d extending therefrom respectively.

In order to prevent any appreciable amount of light emanating from theelectrodes 16 and 18, when each of them glows, from reaching thelight-sensitive elements 22 or 26 respectively, While permitting lightfrom each of those electrodes to reach and actuate the light-sensitiveelements 26 and 22 respectively, the inner walls of the aperture 4 arerendered opaque, in order to ensure that as much light as possibleemanating from the proper electrode 16 or 18 impinges upon the lightsensitive portion of the elements 26 and 22, the inner walls of theapertures and 12 may be made light-reflective. if the material of whichthe housing 2 is formed is itself opaque, the inner walls of theaperture 4 will be inherently opaque, but if the housing 2 is formed oflighttransrnissive material, a suitable opaque coating may be applied tothe inner walls of the aperture 4. If the inner walls of the apertures16 and 12 are, by reason of the material of which the housing 2 isformed, inherently light-reflective, no further treatment is required,but if that is not the case a coating of suitable lightreflectivematerial may be placed on the inn-er surfaces of the apertures 10 and12. The result is that when the electrode 16 glows, as will be the casewhen it is sufficiently negative relative to the electrode 18, lightwill pass therefrom through the slot 6 to the aperture 10, impingingupon and actuating the light-sensitive element 26, while substantiallyno light from the glowing electrode 16 will pass through the slot 8 andimpinge upon the light-sensitive element 22. In this regard it ispreferred that the slot 8 be no wider than a projection of the electrode18 thereon, so that the slot 8 will be in the shadow of the electrode 18which is cast when the electrode 16 is illuminated. Similarly, when theelectrode 18 is illuminated, as will be the case when an appropriatenegative potential is applied thereto relative to the electrode 16,substantially all of the light from the electrode 13 will pass throughthe slot 8 and actuate the light-sensitive element 22, and substantiallyno light from the electrode 18 will reach the light-sensitive element20.

The specific nature of the light-sensitive elements 26 and 22 may bevaried, providing only that they are sufficiently sensitive to thepresence or absence of light to control external circuitry The use ofPNPN silicon diodes for this purpose is highly desirable, not onlybecause such devices are highly light-sensitive and are quite reliable,but also because they have an inherent latch- .ing effectwhen asufficient amount of light impinges on such a device, the device isrendered conductive, and then will remain conductive, even if the lightis removed therefrom, for so long as appropriate electrical potential isapplied thereacross. When that potential is removed the device revertsto its non-conducting state, and will remain in that non-conductingstate until again activated by light. In this way a utilization circuitconnected to such a device may be rendered operative by light, theutilization circuit remaining in that operative status even after theinitiating light impulse is no longer present.

FIG. 3 illustrates a circuit in which the assembly of FIGS. 1 and 2 maybe utilized. Each of the light-sensitive elements 20 and 22 is connectedin series with a different utilization circuit, generically designatedby the resistances 24 and 26 respectively. The light-sensitive element20 and its utilization circuit 24 are connected between power terminals28 and 3t}, and the light-sensitive element 22 and its associatedutilization circuit 26 are similarly connected between a pair of powerterminals which, for purposes of convenience, may be the same terminals28 and 30. A commutating capacitor 32 is connected between correspondingends of the light-sensitive elements 20 and 22 respectively. The controlsignal is applied across terminals 34 and 36, which are connectedrespectively to the electrodes 16 and 18 of the glow discharge tube 14.A resistance 38 may be connected in series in the control circuit, and acapacitor 40 may be connected between the electrodes 16 and 18.

Considering that the terminal 28 is positive and the terminal 3d isnegative, the circuit of FIG. 3 will function as follows: At the start,when no light has reached either of the elements 20 or 22, they both arenon-conductive and no effective current will pass through either of theutilization circuits 2d and 26. If now an appropriate signal is appliedacross the terminals 34 and 36, with the terminal 36 positive withrespect to the terminal 34, the electrode 16 will glow, light willimpinge upon the light-sensitive element 2%}, it will become conductive,and work current will pass thereth-rough and through the utilizationcircuit 24 associated therewith. The right hand side of capacitor 32will become negative and the left hand side of the capacitor 32 willbecome positive. This situation will continue, with current flowingthrough the utilization circuit 24, While the electrode 16 continues toglow. If the control signal is removed and the electrode 16 stopsglowing, there will be no change in the status of the utilizationcircuitscurrent will continue to flow through circuit 24 and no currentwill flow through circuit 26.

If now the control signal is reversed, the terminal 34 becoming positiveand terminal 36 becoming negative, the electrode 18 will glow, lightwill impinge upon lightsensitive element 22, and it will becomeconductive, causing current to pass through the utilization circuit 26associated therewith. This will cause the capacitor 32 to discharge andbecome charged in the opposite direction, applying a negative pulse tolight-sensitive element 26 and therefore unlatching it-causing it tobecome non-conductive. Thereafter, while the electrode 18 continues toglow and even after the control signal has been removed and theelectrode 18 stops glowing, the lightsensitive element 22 will remainconductive and lightsensitive element 20 will remain non-conductive, sothat work current will flow through the utilization circuit 26 and nowork current will flow through the utilization circuit 24.

Since the glowing of the electrodes 16 and 18 follows substantiallyinstantaneously upon the appropriate energization thereof, and since thereaction of the light-sensitive elements 20 and 22 to light impingingthereon is substantially instantaneous, switching action in theutilization circuits 24 and 26 is extremely rapid, on the order of 1 or2 milliseconds. Thus, by controlling the polarity of the signal appliedto the terminals 34 and 36 rapid and reliable switching of theutilization circuits 24 and 26 is effected.

The circuit of FIG. 3 exhibits a unique characteristic which is veryuseful in many circumstances. If the control signal applied across theterminals 34 and 36 were to alternate sufficiently rapidly, theelectrodes 16 and 18 would alternately glow so rapidly that bothlight-sensitive elements 20 and 22 would be rendered conductive at thesame time. Hence, by controlling the nature of the control signalapplied-D.C. in one sense, DC. in the other sense, or relatively rapidA.C.-one can selectively achieve the encrgization of one utilizationcircuit or the other or both simultaneously. The same characteristic ofthe circuit of FIG. 3 could be used to provide a safety factor-amalfunction in a controlled machine or the existence of some externalevent such as fire could so affect the control signal as to cause bothof the utilization circuits 24 and 26 to conduct simultaneously, and theresultant drawing of a high current from the power terminals 28 and 36could actuate an alarm or perform some other appropriate controlfunction.

The assembly of FIG. 1, which includes all of the operative controlparts of the system here described, is disclosed in more or lessidealized form. As disclosed,

it will be apparent that the glow discharge tube 14 and thelight-sensitive elements 20 and 22. are mounted in protected condition,so that they are exceptionally resistant to shock, vibration or thelike. The assembly may readily be encapsulated or otherwise enclosed soas to protect it against humidity, corrosive atmospheres, or otherdeleterious external influences. Electrical connections may readily bemade to the operative parts thereof, and the assembly is well adapted tobe incorporated, either on a breadboard or production basis, into a Widevariety of overall systems or apparatus. There are no moving parts andno current-carrying contacts which might arc, bounce or chatter. Thereare no magnetic fields which might adversely affect adjacent circuitry.The system and assembly is simple and reliable.

While but a single embodiment of the present invention has been herespecifically disclosed, it will be apparent that many variations may bemade therein, all within the scope of the present invention as definedin the following claims.

I claim:

1. A photoelectric switching system comprising a glow discharge tubehaving first and second electrodes and the characteristic that only oneof said electrodes glows at a time depending upon its polarity when D.C.energization is applied to said tube, means for selectively operativelyenergizing said discharge tube with a polarity of one sense or theother, first and second light sensitive latching-type rectifiers inoperative optical relation to said first and second electrodesrespectively, first and second output circuits each comprising a D.C.source, a ditferent one of said rectifiers, and a load electricallyconnected to one another, and a capacitor electrically connected betweencorresponding ends of said first and second rectifiers.

2. In combination with the system of claim 1, a polarized photoelectricassembly comprising a housing having a primary aperture, first andsecond outer stations, and first and second light path means extendingsubstantially from separated portions of said primary aperture to saidfirst and second outer stations respectively, said glow discharge tubebeing in said primary aperture with its first and second electrodes inoperative optical registration with said first and second light pathmeans respectively, said first and second light sensitive latching typerectifiers comprising first and second light sensitive elements in saidfirst and second outer stations respectively and in operative opticalregistration with said first and second light path means respectively,and means for substantially preventing light from said first and secondelectrodes from reaching said second and first light sensitive elementsrespectively.

3. In combination with the system of claim 1, a polarized photoelectricassembly comprising a housing having a primary aperture, first andsecond outer stations and first and second slots extending substantiallyfrom separated portions of said primary aperture to said first andsecond outer stations respectively, said glow discharge tube being insaid primary aperture with its first and second electrodes in operativeoptical registration with said first and second slots respectively, andsaid first and second light sensitive latching type rectifierscomprising first and second light sensitive elements in said first andsecond outer stations respectively and in operative optical registrationwith said first and second slots respectively, the walls of at leastsome of said slots and aperture being opaque, said slots definingsubstantially the sole light transmissive paths between said primaryaperture and said outer stations respectively.

4. In combination with the system of claim 1, a polarized photoelectricassembly comprising a housing having a primary aperture, first andsecond outer apertures and first and second light path means extendingsubstantially from separated portions of said primary aperture to saidfirst and second outer apertures respectively, said glow discharge tubebeing in said primary aperture with its first and second electrodes inoperative optical registration with said first and second light pathmeans respectively, said first and second light sensitive latching typerectifiers comprising first and second light sensitive elements in saidfirst and second outer apertures respectively and in operative opticalregistration with said first and second light path means respectively,and means for substantially preventing light from said first and secondelectrodes from reaching said second and first light sensitive elementsrespectively.

5. In combination with the system of claim 1, a polarized photoelectricassembly comprising a housing having a primary aperture, first andsecond outer apertures, and first and second slots extendingsubstantially from sepa rated portions of said primary aperture to saidfirst and second outer apertures respectively, said glow discharge tubebeing in said primary aperture with its first and second electrodes inoperative optical registration with said first and second slotsrespectively, said first and second light sensitive latching typerectifiers comprising first and second light sensitive elements in saidfirst and second outer apertures respectively and in operative opticalregistration with said first and second slots respectively, the walls ofat least some of said slots and apertures being opaque, said slotsdefining substantially the sole light transmissive paths between saidprimary aperture and said outer apertures respectively.

6. A photoelectric switching system comprising a glow discharge tubehaving first and second electrodes and the characteristic that only oneof said electrodes glows at a time depending upon its polarity when D.C.energization is applied to said tube, means for selectively operativelyenergizing said discharge tube with a polarity of one sense or theother, first and second light sensitive PNPN rectifiers in operativeoptical relation to said first and second electrodes respectively, firstand second output circuits each comprising a D.C. source, a differentone of said rectifiers, and a load electrically connected to oneanother, and a capacitor electrically connected between correspondingends of said first and second rectifiers.

7. In combination with the system of claim 6, a polarized photoelectricassembly comprising a housing having a primary aperture, first andsecond outer stations and first and second light path means extendingsubstantially from separated portions of said primary aperture to saidfirst and second outer stations respectively, said glow discharge tubebeing in said primary aperture with its first and second electrodes inoperative optical registration with said first and second light pathmeans respectively, said first and second light sensitive PNPNrectifiers comprising first and second light sensitive PNPN elements insaid first and second outer stations respectively and in operativeoptical registration with said first and second light path meansrespectively, and means for substantially preventing light from saidfirst and second electrodes from reaching said second and first lightsensitive elements respectively.

8. In combination with the system of claim 6, a polarized photoelectricassembly comprising a housing having a primary aperture, first andsecond outer stations and first and second slots extending substantiallyfrom separated portions of said primary aperture to said first andsecond outer stations respectively, said glow discharge tube being insaid primary aperture with its first and second electrodes in operativeoptical registration with said first and second slots respectively, andsaid first and second light sensitive PNPN rectifiers comprising firstand second light sensitive PNPN elements in said first and second outerstations respectively and in operative optical registration with saidfirst and second slots respectively, the walls of at least some of saidslots and aperture being opaque, said slots defining substantially thesole light transmissive paths between said primary aperture and saidouter stations re spectively.

9. In combination with the system of claim 6, a polarized photoelectricassembly comprising a housing having a primary aperture, first andsecond outer apertures and first and second light path means extendingsubstantially from separated portions of said primary aperture to saidfirst and second outer apertures respectively, said glow discharge tubebeing in said primary aperture with its first and second electrodes inoperative optical registration with said first and second light pathmeans respectively, and said first and second light sensitive PNPNrectifiers comprising first and second light sensitive PNPN elements insaid first and second outer apertures respectively and in operativeoptical registration with said first and second light path meansrespectively, and means for substantially preventing light from saidfirst and second electrodes from reaching said second and first lightsensitive elements respectively.

10. In combination with the system of claim 6, a polarized photoelectricassembly comprising a housing having a primary aperture, first andsecond outer apertures, and first and second slots extendingsubstantially from separated portions of said primary aperture to saidfirst and second outer apertures respectively, said glow discharge tubebeing in said primary aperture with its first and sec ond electrodes inoperative optical registration with said 3. first and second slotsrespectively, and said first and sec- 0nd light sensitive PNPNrectifiers comprising first and second light sensitive PNPN elements insaid first and second outer apertures respectively and in operativeoptical registration with said first and second slots respectively, thewalls of at least some of said slots and apertures being opaque, saidslots defining substantially the sole light transmissive paths betweensaid primary aperture and said outer apertures respectively.

References tilted by the Examiner UNITED STATES PATENTS 2,208,147 7/1940Eislen 250-228 X 2,727,683 12/1955 Allen et al 250-209 X 2,790,0884/1957 Shive 307-885 2,967,945 1/1961 De Gier 250-211 X 2,997,596 8/1961Vize 250-209 3,066,258 11/1962 Van Overbeek et al. 307-885 3,143,6558/1964 Strandberg 250-239 RALPH G. NrLsoN, Primary Examiner. WALTERSTOLWEIN, Examiner.

1. A PHOTOELECTRIC SWITCHING SYSTEM COMPRISING A GLOW DISCHARGE TUBEHAVING FIRST AND SECOND ELECTRODES AND THE CHARACTERISTIC THAT ONLY ONEOF SAID ELECTRODES GLOWS AT A TIME DEPENDING UPON ITS POLARITY WHEN D.C.ENERGIZATION IS APPLIED TO SAID TUBE, MEANS FOR SELECTIVELY OPERATIVELYENERGIZING SAID DISCHARGE TUBE WITH A POLARITY OF ONE SENSE OR THEOTHER, FIRST AND SECOND LIGHT SENSITIVE LATCHING-TYPE RECITIFIERS INOPERATIVE OPTICAL RELATION TO SAID FIRST AND SECOND ELECTRODESRESPECTIVELY, FIRST AND SECOND OUTPUT CIRCUITS EACH COMPRISING A D.C.SOURCE, A DIFFERENT ONE OF SAID RECTIFIERS, AND A LOAD ELECTRICALLYCONNECTED TO ONE ANOTHER, AND A CAPACITOR ELECTRICALLY CONNECTED BETWEENCORRESPONDING ENDS OF SAID FIRST AND SECOND RECTIFIERS.